Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 180727
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
327 AM EDT Fri Aug 18 2017

.SYNOPSIS...
Cold front Friday. Upper trough Saturday. High pressure through
Tuesday. Strong cold front mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 255 AM Friday...

Even though we have a significant upper trough crossing the Ohio
Valley with a cold front today, timing of the front along with
the strength and axis of QPF with this system is not that easy.
First, this is still summer, so trying to time the cold front
with the upper trough will be difficult, and models do have a
good piece of its main energy lifting up across Ohio and
Pennsylvania. Will adjust frontal movement a bit faster than
the models today, aided by mixing with stronger west winds
aloft with diurnal heating.

Given this scenario, timing would have the front along the Ohio
River around noon, central WV around 3 PM, and exiting the
mountains early this evening. Convergence along the front is not
impressive to be the main focus of activity. On the other hand,
it looks like a well defined upper disturbance within this
upper trough ahead of the front over south central KY will be
the main focus for convection today, as it lifts northeast
across our area. With PW`s above 2 inches and the atmosphere
conditionally unstable, it wont take much to fire off
convection. Indeed, models do paint significant convection,
especially northwest two thirds of the area, with this upper
feature. Some of the storms will have locally heavy rain, but no
significant water problems or severe thunderstorms are expected
today. So, we have pops starting out high along the Ohio River
early this morning, then shifting east northeast across the area
today. Note that much of southeast Ohio will escape convection
with this feature, having already been affected by another
disturbance last evening.

Most of the convection will be over eastern WV by mid
afternoon, but will still carry a small pop until the front
passes. In any case, convection will exit the mountains this
evening as drier high pressure and clearing skies move in for
tonight. So we may have to evaluate for a good river valley fog
later Friday night. Temperatures will be tempered today with the
clouds and showers, but will be humid ahead of the front.
Cooler tonight with the clearing and drier air.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
As of 240 AM Friday...

Upper level trough brings another batch of showers/storms
through primarily the northern half of the forecast area
Saturday before the long wave pattern goes back to ridge
dominant over the southeastern US. This ridge will bring higher
heights over the region, with temperatures back into the upper
80s to lower 90s for the lowlands through the weekend and into
the beginning of next week. Expecting mainly dry weather after
Saturday

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 240 AM Friday...

Long term operational models showing some consistency in the
development of a closed low over the Canadian prairies that will
drop into the Great Lakes for the middle of next week.
Associated cold front will bring the Ohio Valley and central
Appalachians back into a cooler and drier airmass in a more
amplified ridge/trough pattern from west to east across the
CONUS. CPC outlook is supportive of the operational model
solutions as of this point with chances for below normal temps
embedded in the northeast quadrant of the lower 48.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
06Z Friday thru 06Z Saturday...
As of 145 AM Friday...

An upper disturbance and cold front will move east across the
area today, bringing showers and TSTMS. Most of the convection
will be in an organized band ahead of the front itself with the
upper disturbance, lasting about a 3 to 4 hour period in any
location. The front will lag behind this band, so continue
scattered convection until the front actually passes. The front
will likely reach the Ohio River around 16Z, a CKB-CRW line
around 20Z, and exiting the mountains around 00Z.

Fog early this morning will be limited mostly to the protected
valleys of the mountains, affecting EKN til around 10Z when the
clouds move in.

Outside of convection, look for VFR ceilings, lowering to MVFR
ceilings/vsby in convection, but locally IFR in the heaviest
convection in the main band. Behind the front, becoming SCT-BKN
4000-6000 feet AGL thru the afternoon. With loss of heating and
high pressure building in, look for rapid clearing from west to
east early this evening. With mostly clear skies setting in
tonight, fog appears likely after 06Z Saturday at the major TAF
sites.

Generally south to southwest winds 5 to 10 KTS ahead of the
front today, becoming westerly at the same speeds behind the
front, then light and variable tonight.


FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SATURDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing and coverage of showers and
thunderstorms could vary. Some fog can not be ruled out in the
mountain valleys early this morning.


EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH:   TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW:    TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

DATE                              FRI 08/18/17
UTC 1HRLY       06   07   08   09   10   11   12   13   14   15   16   17
EDT 1HRLY       02   03   04   05   06   07   08   09   10   11   12   13
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    M    M    L
HTS CONSISTENCY  H    H    M    M    H    M    H    M    H    L    L    L
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    L    H    L
EKN CONSISTENCY  H    H    H    L    M    M    M    L    H    M    M    L
PKB CONSISTENCY  M    M    M    L    M    M    M    M    M    H    H    L
CKB CONSISTENCY  M    H    H    H    H    H    M    H    H    M    M    L

AFTER 06Z SATURDAY...
Dense river valley fog possible each morning.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...JMV/26
NEAR TERM...JMV
SHORT TERM...26
LONG TERM...26
AVIATION...JMV



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